Metal plating by successive addition of plating ingredients



J. G. SIMON Aug. 23, 1966 2 Sheets-Sheet 1 Original Filed Feb. 28, 1959 FIG. I

- ALL MATERIAL ADDED INITIALLY 6 5 4 CZuU mun: mbm a omkl a mIk O 220 PIOGB INCREMENT ADDITION 2.5 MIN.

-INCREMENT ADDITION IO MIN.

3O 40 TIME (MINUTES) JOHN G. SIMON ATTORNEY COATING THICKNESS (INCHES) METAL PLATING BY SUCCESSIVE ADDITION OF PLATING INGREDIENTS Original Filed Feb. 28, 1959 2 Sheets-Sheet 2 Aug. 23, 1966 J. G. SIMON FIG. 2

0.0005 ALI MATERIAL ADDED INITIALLY -INCREMENT ADDITION IO MIN. -INCREMENT ADDITION 6 MIN. INCREMENT ADDITION 2.5MIN.

I I I I I 0 IO TIME (MINUTES) JOHN G. SIMON INVENTOR.

ATTORNEY United States Patent i 6 Claims. (Cl. 117-109) This application is a division of application Serial No. 789,544, filed January 28, 1959, and now abandoned.

This invention relates to processes of plating by application of mechanical forces to particulate malleable metals and mixtures and alloys thereof, in order that such metals shall be caused to adhere to substrate surfaces.

It is known in the art to plate a metal upon a substrate which is usually itself metal, by applying to the said plating metals, which are in the form of blocky, minute, malleable particles, mechanical forces sufficient to produce such a close association of the plating metal particles and the surface of the article to be plated, that adhesion occurs between the substrate surface and the plating metal particles.

Methods have been developed whereby the mechanical forces necessary to produce such adhesion are derived from the placing together of the articles to be plated, the plating metal particles, solid impacting media and some substances found to be effective in the promoting of such plating, in a ball mill or tumbling barrel, and rotating together, so that the kinetic energy of the moving impacting media is transferred to the plating metal particles in such a way that the plating metal particles are hammered or pounded by the impacting media onto the surfaces of the articles to be plated. In some cases, the articles to be plated have acted as their own impacting media, serving to strike in their motion resulting from the barrels rotation, and to compact and to hammer plating metal particles against other articles. While such methods have worked in a limited way, they have been inefficient and have, in many cases, failed to produce a desirably great degree of adhesion between the metal plating and the substrate. Also, the plating which has been produced by this general method has been uneven, spongy, loosely compacted and lumpy in its build up, so that the density of the plating has been inconsistent throughout.

It is an object of this invention to regulate the rate of deposition of plating metal particles on the substrate such that there is not accumulated at any one time a greater number of plating metal particles than can be distorted and flattened and cold welded to the substrate, and to the underlying and adjacent plating metal particles, by the mechanical energy made available by suitable impacting forces.

It is a further object of this invention to provide an article having a solid surface upon which has been deposited by mechanical means, a ductile, chip-resistant and flake-resistant plating built up from plating metal particles which are uniformly disposed upon and about the sur face of the article, which plating is highly cohesive, uniform and tightly compact, tenaciously adhered to the surface of the substrate article, and has a bright metallic lustre.

Another object of the invention is to provide a process step whereby it is possible to produce a mechanically applied metal plating upon a substrate, which plating has significantly increased adherence to the substrate and greater compaction, cohesion and uniformity of distribution over the surface of the substrate than heretofore possible to produce by mechanical methods and means.

A still further object of the invention is to provide in 3,263,356- Patented August 23, 1966 a solid form, a material which will, when dissolved or disintegrated in the presence of a liquid medium, regulate the rate of deposition of plating metal particles on the substrate and promote the producing of such high quality platings as are hereinabove referred to.

Still other and further objects of the invention will become apparent as this disclosure progresses.

The principal work in the field of mechanical plating of the type described above has been done by Clayton and Pottberg, whose most conspicuous developments are described in US. Patents Nos. 2,640,001, 2,640,002, Re. 23,861; 2,689,808; 2,723,204, etc. In all of the methods and processes which they disclose, the essential steps set forth in the second and third paragraphs of this disclosure are carried out. Sometimes this is done in the absence of liquids, but more often, there are liquids present, and the agitated conglomerate or slurry contains what are referred to as promoter chemicals. These latter usually comprise unsaturated fatty acids and the like, film forming materials and surfactants. While these promoter chemicals do benefit the general process involved, it has been my experience that the simple fact of their presence is not sufficient to assure a process which will accomplish metal plating of the high quality or with the great efliciency to which this invention is addressed.

It was found that, where adequate amounts of the promoter chemicals were included in the original barrel charge so that the plating metals would plate to exhaustion or nearly so, there occurred, at least where the promoter chemicals were used according to the teaching of prior patents, the accumulation of such a thick and mushy plate early in the agitating (tumbling) operation that, while plating metal particles were certainly being applied to the surface of the article it was desired to plate, they were being accumulated thereon at an uncontrolled and too rapid rate, and were not being exposed to sufiicient direct hammering by the impacting media with the consequence that the amount of mechanical energy required to distort and compact them was not reaching them. Because of this too-rapid build up of the plating, with a resulting lack of uniformity in the character of the plating, abetted by agglomeration of the plating metal particles, the outer or most recently accumulated plating metal particles were absorbing and dissipating the impacting stresses which are most beneficially applied directly to the inner or first associated plating metal particles, lying nearest the substrate. These hammering or tumbling stresses were then so widely distributed throughout the still soft plating that the inner plating metal particles were actually being shielded, cushioned or insulated from the very forces which it is desired will reach them and hammer them sufficiently so that they will be adequately dis torted and brought into close contact over their resultant large, flattened or semi-flat surfaces with the substrate surface of the article to be plated as well as with adjacent like plating metal particles.

It was discovered that, by regulating the amount of the promoter chemicals, and/ or optionally the plating metal particles at any given period to that necessary to lay down only a thin coat of plating metal particles, the excessive build up rate can be prevented, and in consequence, it is easily possible and practicable to apply sufficient mechanical energy to the plating metal particles of such a thin coat as they are being laid down, that these plating metal particles can be adequately and directly hammered, deformed, distorted and conjoined by the moving impact media and brought into adequately intimate contact with the substrate surface. As a result, the plating so produced is much more firmly adhered to the substrate surface, and is built up from well-hammered,

highly distorted and compacted plating metal particles which are by the direct application of such hammering strasses tightly welded into what appears microscopically to be a remarkably uniform, well-adhered, dense, cohesive plating, in contrast to the plating which is obtained when in accordance with the teachings of the prior art the entire amount of plating metal particles and promoter chemicals are placed in the barrel at one time.

Platings produced by employing the methods herein disclosed are, as measured by accepted standards, equal or superior to electrically deposited platings in their adherence to the substrate surface and far superior to electrically deposited platings in their ductility. The platings I have, by methods using the step disclosed herein, consistently and reproducibly deposited upon articles such as steel wire nails are, in contrast to those on identical nails which have been electroplated and plated by other methods of mechanical plating to commensurate thickness of plate, so uniquely adherent, coherent and ductile that the nails can be bent about a short radius without any evidence of crazing, raising, chipping, flaking, cracking, peeling, spalling or separation of the applied plating.

One of the distinctive results of the step disclosed is that, while other methods of mechanical plating have failed to distribute the plating evenly and uniformly over the surfaces of articles having highly irregular or complex geometric configuration, this step is capable of benefiting the process in which it is incorporated so that one using such process can lay down an evenly distributed and uniform plating over the whole of the surface of the article to be plated. The superiority of the coatings made in accordance with my invention has been established by such test methods as the Preece test (ASTM A239-41), for zinc platings on steel, by microscopic examination of the surfaces and sections of the plated article, and by the time of appearance of rust when zinc or cadmium plated parts are subjected to salt spray tests such as ASTM Bl17-S4T. I have, using this step. with predictable regularity laid down highly adherent and coherent metal platings in the head grooves and threads of screws. Also, I have been able to plate intricately shaped metal fastening devices with satisfactory plating of inside, outside and edge surfaces resulting. While I have repeatedly attempted to accomplish this with prior mechanical plating methods, I have never succeeded.

While my step improves the quality of plating, it also makes possible the production of this superior plating in a shorter time than is required to accomplish the former inferior plating. The reason for this is found in the fact that, employing my step, the mechanical energy of the moving impacting media is, from the very first turn of the barrel until the plating operation is ended, imparted directly and with great effciency to the malleable plating metal particles which are backed up from the direction of the substrate by either the hard substrate itself or, when some plating has been laid down, by less malleable, hard, dense, compact, conjugate layers of the plating metal particles. On the contrary, in the former methods, as has been pointed out, the energy of the moving impacting media is transferred to the outside layer of particles of a relatively thick, quickly accumulated coat of malleable plating metal particles without the benefit of hard, consolidated backing as in my met-bod, and the effect of the hammering stresses imposed on these outer plating metal particles is largely lost, so that little or no deformation or compaction of plating metal particles occurs, except in the outer shell. FIG. 4 shows that the distribution of hammering stresses among the plating metal particles is very even and uniform when the step disclosed herein is used. It will be noted that the degree of deformation of the plating metal particles is great and amazingly uniform. This is highly desirable, as such a plate will resist pin hole effects and the pitting that results from weathering.

In order to fully and efficiently exploit the discovery that the controlled accumulation of the plating metal particles on the substrate during the period of plating was the key to high quality and efficient mechanical plating, it was, of course, necessary that there be devised a method or methods of accomplishing this step. In order to implement the discovery that the rate of accumulation of plating metal particles on the surface of the article to be plated bears correlation with the concentration of the promoter chemical present in the plating slurry and also with the amount of plating metal particles in the slurry, I fell upon a method of controlling the concentration of these ingredients of the slurry in such a way that it would not be necessary (where, for example, a tumbling barrel is used) to stop the various barrel runs, and open the barrel to meter into it the various quantities of materials to be added. I discovered in the course of my Work that the promoter chemical components and/or plating metal particles can be compounded in a solid mixture which, when subjected to varying pressures, can be made into units (such as bars) of varying compaction and density, and that the rate of disintegration of such a unit (bar) into a slurry when immersed in or exposed to liquids is directly related to the density and consequently to the extent of the pressure to which such a unit has been exposed. Thus, by adjusting pressing pressure, the rate of solution or disintegration of the solid may be tailored to fit the plating job to be done.

As has been suggested, it is obvious that no single given thickness, quality or composition is suited to all purposes and requirements of metal platings. I found that by using solid promoter chemical units (bars) of varying compaction and density, one can fill the requirement for such a variety of platings, by preselection. It is a valuable feature of the invention that by using these solid bars or units comprising materials which are useful for mechanical plating, with or Without the inclusion therein of plating metal particles, it is possible in a short time to train a person completely unskilled in the science and techniques of metal plating to carry out the plating operation, whereas Without this step and these materials, the process requires a relatively more highly skilled operator. Persons who were previously unskilled are, with very short periods of training, able to carry out the plating operation so that they produce coatings possessing adhesion of the plate to the substrate, cohesion of the plating itself, and uniformity of compaction, ductility and density of plating which are all highly superior to those of mechanically applied platings produced, even by those skilled in the art, without the use of my step.

The following is a typical formulation of my solid promoter chemical bar:

Parts citric acid 2.5 Part of a polyoxyethylene oleic amide 1.0 Parts attapulgite clay 1.5 Part silicone antifoaming agent .07

Experimentation indicates that some benefit is had from adding the plating metal particles alone slowly to the balance of the complete charge in the barrel, though the benefits are not so great as where the promoter chemical is also added in like manner. Likewise, there is benefit to be had from adding the chemical alone, over at least a portion of the period of the barrels rotation.

FIG. 1 is a graph in which the actual results of two mechanical plating methods are illustrated. The percentage gain in weight of a batch of steel wire nails is plotted against the period of time during which they were agitated in a typical tumbling barrel, under identical conditions, except for the fact that during runs 2 and 3 a part of the promoter chemical (the surfactant) and the zinc particles were added in equal sub-unitary increments. It will be seen that there is a direct and continuing correlation between time and weight gain in the case of the method in which my step occurs. It is obvious that no such direct correlation obtains in the prior art method which omits the present step (run 1 in FIG. 1).

FIG. 2 is a graph in which are portrayed the results of four mechanical metal plating runs using identical zinc plating particles and steel wire nails, and in which the final slurries are made up of identical components. In this graph time in minutes is plotted against plating thickness in inches. It will be seen that in the case in which the complete barrel charge is originally made, there is an extremely steep curve, indicating the early association of a very thick accumulation of uncompacted plating metal particles, while in the case of the runs in which the surfactant and zinc plating particles are added in sub-unitary increments periodically, the curve is not so steep, but increases in steepness with the frequency with which the sub-unitary increments are added. Inasmuch as there is available over the period of time represented by the horizontal ordinate of the graph, only a limited amount of hammering energy, it is obvious that, where the curve has been flattened, the innermost and succeeding accumulations of plating metal particles have been exposed to a greater amount of the direct hammering effect, inasmuch as the hammer blows are distributed over a considerably lesser thickness of accumulated but uncompacted plating metal particles than where the curve is steeper.

This explains why, using the present step, it is possible to obtain superior plating compared to the prior art methods, none of which include my step.

The solid promoter chemical unit for mechanical plating may be produced by incorporating the required chemicals, and/or the cleaning agent, and/or the plating metal particles in a binder. If desired, an anti-foam agent may be added to the bar. As suggested above, the density of the metal plating bar serves as a control of the rate at which the bar is disintegrated in a liquid environment when agitated in a container and thereby as a control of the rate at which the components of the bar are made available to the plating charge. This rate of disintegration indirectly affects the rate of deposition of the particles of plating metals such as cadmium, lead, tin or zinc on the substrate to be plated. Usually the density is regulated by compacting the components of the metal plating bar in a mold. The exact compacting depends upon the given surface area, the specific ingredients employed, the surface characteristics of the substrate, the impact media, the size of the tumbling container, the vigor of agitaiton and temperature of the solution. This controlled release of the ingredients from the solid unit made possible by the use of the disintegrable solid form of the promoter chemical, etc. can also be achieved by other means of regulating the rate of disintegration of the compacted solid, as for example by use of disintegrable or soluble capsules or multiple compartments within a bar releasing the surfactant or other ingredients into the plating slurry when the encapsulating ability of a compartment has been destroyed.

Such metal plating bars of controlled disintegration can be made, e.g., by mixing and compacting 2-20 parts anhydrous citric acid with 1-10 parts polyoxyethylene oleic amide, 0.01-5 parts silicone anti-foam agent, and 1-50 parts of a hydrophilic, argillaceous powder such as attapulgite clay. This mixture is then compacted, e.g., at 250 to 750 pounds per in. gauge into a convenient shape, e.g., a right circular cylinder. Such compacting is adjusted to permit disintegration of a 1 in. diameterx 0.4 in. high cylinder of said compacted mixture at a rate of 2 to volume percent per minute when tumbled in a 1.2-gallon hexagonal tumbling barrel at 50 r.p.m. together with 0.5 gallon of 20-50 mesh glass beads (impacting media) and 0.5 gallon of Water at 70 F., and this rate of disintegration has been effective in operating the regulated concentration step of the present invention in given cases.

The metal plating bar above described may also contain minute plating metal particles for controlled release into the charge. These metal particles can be admixed with other ingredients. To avoid contamination, oxidation or other types of reaction, the plating metal particles may receive a protective coating, such as a plastic or resinous coating, abradable by agitation and impact, or they can be incorporated into the bar in the form of disintegrable plastic pellets or capsules, which capsules form a barrier between the metal and the other ingredients.

The above described metal plating bar may also be made or equipped with an outer shell containing the required impact media so that all components of the plating charge with the exception of the liquid and the articles to :be plated are readily available in one package.

The following examples are offered as a better understanding of the present invention and are not to be construed as unnecessarily limiting thereto.

EXAMPLE I 1362 grams of 6d common steel wire nails were placed into a 1.2-gallon hexagonal, plastisol-lined steel tumbling mill. The nails had previously been cleaned by soaking of 5 minutes in an alkaline solution, pH of 13, at to F after rinsing, the nails were pickled for one minute in hydrochloric acid (1 part 38% HCl to 5 parts of water) at 170-190 -F.; thereafter, the nails had been flash-coated with copper by immersion for 15 seconds in a solution of 0.24 l-b./ gal. Cuprodine salt (inhibited copper sulfate) and 113 ml./ gal. sulfuric acid and, thereafter, rinsed. The mill was then charged as follows:

(a) Impact media: 1362 grams of glass beads in various sizes ranging from 20 to 50 mesh (b) Anti-foam agent: 1 gram silicone (c) Cleaning agent: 12 grams anhydrous citric acid (d) Surfactant: 1 gram polyoxyethylene oleic amide (e) Metal: 17 grams zinc powder with a median particle size of 8 microns (f) Water: at 50 F. to cover charge The mill was then closed and agitated by rotation at 75 r.p.m. for 10 minutes after which the charge was regenerated by adding an equal increment of (d) and (e); at 10-minute intervals, 4 further increments of (d) and (e) were added. After a total of 60 minutes of incremental addition and agitation the mill was stopped; the parts were separated from the impact media and washed; subsequentially all the metal had been deposited on the nails; they had a lustrous coating of zinc averaging 0.0022" thick, as measured by the Magnagauge brand instrument for measuring plating thickness. Samples were subjected to a bend test by bending a nail about a A" radius. The coating did not flake, crack or raise until bent in excess of 170 thereby demonstrating its superior adhesion and cohesion.

EXAMPLE II 1362 grams of 6d wire iron nails, after receiving the identical surface treatment as in Example I, were placed in an identical tumbling mill. The mill was then charged as follows:

(a) Impact media: 1362 grams of glass beads in various sizes ranging from 20 to 50 mesh (b) Anti-foam agent: 1 gram silicone (0) Cleaning agent: 13.5 grams citric acid in aqueous solution (d) Surfactant: 5.5 grams polyoxyethylene oleic amide in aqueous solution (e) Metal: 100 grams of zinc powder with a median particle size of 8 microns (f) Water: at 50 F., to cover charge (c) and (d) were in an aqueous solution.

The mill was then closed and agitated by rotation at 75 r.p.m. for one hour. Thereafter, the mill was stopped, the parts separated from the impact media and washed. About 90% of the metal had been deposited on the nails, which had a bright Zinc coating of a thickness averaging 0.00275". Samples were subjected to a bend test by aaeseee bending a nail about A" radius. The poor adhesion and cohesion were demonstrated as the coating flaked and cracked at less than 30 bending. The coating of the head of a sample nail spalled olf when the nail was hammered into a fir wood board. Poor uniformity, adhesion and cohesion were the indirect result of the immediate availability of all the ingredients in the plating charge. This immediate availability (excessive concentration) caused all of the plating metal particles to be very rapidly deposited upon the surfaces of the nails. Superior performance characterized the nails of Example I, plated with substantially identical ingredients but with regulation of the rate of deposition of the plating metal particles.

EXAMPLE Ill 4,000 grams of steel machine screws (size 10-32) were prepared in exactly the same manner as those in Example IV. The same mill was used as in Example II. The mill was charged as follows:

(a) Impact media:

1400 grams 4-8 mesh non-spherical glass media 700 grams 14-20 mesh non-spherical glass media 350 grams 70-80 mesh glass beads (b) Anti-foam agent: /2 gram silicone (c) Cleaning agent: 15 grams citric acid, anhydrous (d) Surfactant: 5 grams polyoxyethylene oleic amide (e) Metal: 60 grams zinc with a median particles size of 3.0 microns diameter (f) Water: at 50 F. in sufficient quantity to cover the charge by one inch The mill was closed, agitated by rotation at 54 rpm. for 50 minutes. Results: All zinc had been deposited on the screws. However, the plating was very uneven and lacked uniformity. For example, some of the screws had a heavy spongy coating over 90% of the surface area. Large amounts of spongy zinc had plated out in the threads, filling them to a depth which made it impossible to thread the bolt into a matching set of threads. On the same screw, the slot in the head was bare of zinc, and the underside of the head was about 50% covered with Zinc. Another screw from the same run had zinc on less than 80% of its surface. The rounded surface of the head was the only portion where an appreciable amount of zinc plated and here the coverage was not more than 50%. On other screws in the run, the results were intermediate between the extremes described.

EXAMPLE IV 4,000 grams of steel machine screws (size -32) were preparedfor plating by degreasing in a strong alkaline solution. The parts were then rinsed and given a thin copper coating by immersion in an acidified Cup-Iodine salt (inhibited copper sulfate) solution for 30 seconds. After rinsing, the parts were placed in a mill which was charged as follows:

(a) Impact media:

1400 grams 4-8 mesh non-spherical glass media 700 grams 14-20 mesh non-spherical glass media 350 grams 70-80 mesh glass beads (b) Anti-foam agent: /2 gram silicone (0) Cleaning agent: 15 grams citric acid, anhydrous (d) Surfactant: 1 gram polyoxyethylene oleic amide (e) Metal: 12 grams zinc with a median particle size of 3.0 microns diameter (f) Water: at 50 F. in sufficient quantity to cover the charge by one inch The mill was then closed. The charge Was agitated by rotation for ten minutes at 54 r.p.m., at which time the mill was stopped, the mill opened and the charge was re plenished by adding a second, identical increment of (d) and (e). Again, the mill was rotated for 10 minutes. This cycle was repeated until four identical incremental additions of (d) and (e) had been made subsequent to the original charge.

The results at the end of 50 minutes rotation showed the parts to have been plated over their entire surface including the thread roots and the recessed head slot. No exact coating measurements could be made because of surface geometry, but the thickness of coating was estimated to be approximately 0.0005". Visual inspection showed bright appearance and superior coating uniformity.

EXAMPLE V 2700 grams of 6d common steel wire nails were placed into a 1.2-gallon, hexagonal, plastisol-lined steel tumbling mill. The nails had been previously cleaned, pickled and copper-flashed as described in Example I. The mill was then charged as follows:

(2.) Impact media: 2700 grams of glass beads in various sizes ranging from 20 to 50 mesh (b) Metal: 210 grams of zinc particles with a median particle size of 8.0 microns (c) Water: at 50 F to cover charge (d) Metal plating bar:

27 grams of a solid bar of promoter chemical having the composition of 2.5 parts citric acid 1 part of a polyoxyethylene oleic amide 1.5 parts of an attapulgite clay 0.07 part of a silicone, anti-foam agent The said metal plating bar was molded in a mold of approximately 1.3 inch diameter and 1 inch in height and subjected to 800 pounds per square inches pressure. The mill was then closed and rotated for 60 minutes.

After 60 minutes of rotation a plating of 0.003 inch had been deposited on the nails and in order to determine adhesion of the plating, they were bent around a V2 inch radius; their plating did not spall or flake demonstrating excellent adhesion.

The Preece test was then employed to determine the uniformity of the plating. After four 1 minute dips no failure of the plating was observed.

Comparative barrel plating runs under identical conditions, using 27-gram solid metal plating bars of like composition, but diiferent pressing pressures were made.

To the nails in each of the 4 plating runs 0.003 inch plating of zinc had been applied after the 60 minutes of rotation. These nails Were then tested for adhesion of the plating and uniformity of the plating by identical test procedures.

The following table shows these test results:

As used throughout this application, the following terms are given the meanings set opposite them below:

Conjugate" refers to fusing, uniting or adhering to one another of plating metal particles.

Ductile" as used herein describes the ability of a metal plate to be stretched or drawn, as being bent about a short radius, without cracking, crazing, spa-lling, flaking, or separating.

Plating metal is a metal which is applied to the surface of an article and which ultimately assumes the form of a plating or skin. This metal is applied in the form of minute particles.

Promoter chemicals are chemical substances useful in the promoting of mechanical plating, but not necessarily involved in chemical reactions in the mechanical plating process.

Slow addition refers to adding at least a portion of the plating metal particles and/or promoter chemical to the balance of the whole plating slurry over at least a part of the period of the plating operation.

Slowly disintegrable describes solid and semi-solid and colloidal materials including inter alia mixtures, which substantially and ultimately substantially lose their cohesiveness when intimately exposed to a liquid which wets them. This term also comprehends those solid substances, including inter alia mixtures, which fall apart when mechanically agitated.

Sub-unitary or sub-unitarily as used herein relates to less than the whole.

I claim:

1. The process of mechanically plating parts with a plating metal which comprises placing in a plating barrel said parts, liquid, plating metal particles, and chemical plating promoter, at least one of the last two named ingredients being initially available in insufficient amount to achieve the desired metal plating, agitating the contents of said barrel throughout a plating cycle, and adding over a substantial portion of said plating cycle the remainder of each initially insufficient ingredient.

2. The process of claim 1 wherein the parts are metallic.

3. The process of claim 2 wherein the liquid is water.

4. The process of claim 3 wherein the chemical plating promoter is initially available in insuificient amount.

5. The process of claim 3 wherein the plating metal particles are initially available in insufficient amount.

6. The process of claim 3 wherein both the chemical plating promoter and the plating metal particles are initiaL ly available in insufficient amount.

References Cited by the Examiner UNITED STATES PATENTS Re. 23,861 8/1954 Clayton 117-109 111,882 2/1871 Smith 117-109 940,593 11/1909 Hardman 117-109 1,911,761 5/1933 Loomis et a1. 2,436,766 2/1948 Davis 117-109 X 2,640,001 5/1953 Clayton 117-109 2,640,002 5/ 1953 Clayton 117-109 2,689,808 9/1954 Clayton 117-109 X 2,723,204 11/1955 Pottberg 117-109 X 2,999,767 9/1961 Clay et al 117-109 3,023,127 2/1962 Clayton 117-109 3,093,501 6/1963 Clayton 117-31 X 3,132,043 5/1964 Clayton 117-109 WILLIAM D. MARTIN, Primary Examiner.

H. E. COLE, W. D. HERRICK, Assistant Examiners. 

1. THE PROCESS OF MECHANICALLY PLATING PARTS WITH A PLATING METAL WHICH COMPRISES PLACING IN A PLATING BARREL SAID PARTS, LIQUID, PLATING METAL PARTICLES, AND CHEMICAL PLATING PROMOTER, AT LEADT ONE OF THE LAST TWO NAMED INGREDIENTS BEING INITIALLY AVAILABLE IN INSUFFICIENT AMOUNT TO ACHIEVE THE DESIRED METAL PLATING, AGITATING THE CONTENTS OF SAID BARREL THROUGHOUT A PLATING CYCLE, AND ADDING OVER A SUBSTANTIAL 